The present invention relates to a sizing agent suitable for use in paper making, and more particularly to a paper sizing agent comprising a substituted succinic anhydride and an emulsifier, which is capable of exhibiting an excellent sizing effect even after stored for a long term.
Various materials have been used for sizing paper. In recent years, sizing using a dicarboxylic acid anhydride has been proposed.
Dicarboxylic acid anhydrides such as substituted succinic anhydrides, which have been used for sizing paper in neutral pH region, have been used usually in the form of an aqueous emulsion by emulsifying in water using an emulsifier such as a surface active agent or cationized starch and a homogenizer or homomixer. It is known that if the dicarboxylic acid anhydride is previously admixed with an emulsifier and stored in the form of a mixture, the emulsifying ability is lowered in a short term and, therefore, the sizing effect is also lowered.
It is an object of the present invention to provide a paper sizing agent comprising a substituted succinic anhydride and an emulsifier, which can exhibit an excellent sizing effect even after stored for a long term.
The above and other objects of the present invention will become apparent from the description hereinafter.